Chronic granulomatous inflammatory diseases, such as tuberculosis, are important clinical problems whose pathogeneses are not clearly understood. Traditionally, cellular defense mechanisms against tubercle bacilli have been considered to involve granulomatous inflammatory response with macrophages being the principal effector cell but mechanisms of recruitment and stimulation of macrophages remain unclear. HYPOTHESIS. Since neutrophils precede the appearance of macrophages at inflammatory sites and can release potent inflammatory mediators, we hypothesized that tubercle bacilli stimulate neutrophils to release chemotaxins which attract monocytes which later differentiate into macrophages and sequester mycobacteria in granulomata. Our preliminary data in a model of TB pleurisy, supported this premise by showing chemotaxins for monocytes in pleural fluid from normal but not neutropenic rabbits and the presence of chemotaxins for monocytes in in vitro mixtures of neutrophils and tubercle bacilli. Furthermore, neutropenia had potentially detrimental consequences including increased numbers of recoverable colonies of tubercle bacilli, decreased granuloma formation and increased pleural fibrosis. Our specific aims are: 1. To determine if tubercle bacilli stimulate neutrophils to make chemotaxins for monocytes in vivo and in vitro. 2. To determine the mechanisms by which chemotaxins for monocytes are formed by neutrophils stimulated by tubercle bacilli. We will evaluate these questions by searching for chemotaxins in parallel experiments in our in vivo models of TB pleurisy and in in vitro, particularly evaluating if chemotaxins isolated in vitro are identical to and have physiological relevance in the in vivo model. We will determine the mechanism of chemotaxin formation by examining if they are performed in neutrophil granules, if oxygen radicals are required for their activation and if protein synthesis is required for their formation. SIGNIFICANCE. This research will give us a better understanding of basic mechanisms operative in granuloma formation and could improve clinical management of granulomatous disease.